The present invention relates to a mining method for deep sea.
WO2012091706 relates to a subsea pressure control system for a well annulus, which system includes s subsea choke which variably restricts flow of drilling fluid from a well annulus to a surface location, the choke being positioned at a subsea location, and a subsea process control system which automatically operates the subsea choke, whereby a desired pressure is maintained in the well annulus.
In general when material is excavated at the seafloor, pumped upward to a vessel and processed, the transported volume mostly contains waste. These will be returned via a pipe downward to the seafloor. In mining, slurry heavier than water will be returned to the seafloor. If the hydrostatic pressure of the slurry column in the return pipe is higher than sum of the friction losses and the water column pressure, than a high risk of vacuum at top of return pipe remains.